The above words are taken from the hymn, Praise to the Lord, and were written by Jaochim Neander, and translated by Catherine Winkworth.  I am not sure why the word if was used.  Certainly God wants us to have no doubt that He has befriended us with limitless love.

Who can doubt this when we know that He laid aside His royal robe and kingly crown, and came to this world in the garb of humanity, that he might stand as [our] substitute and surety?  –Ellen White, Prayer, p. 90

Happily, there is no if.  We can ponder His love anew this season and every day.